diff --git a/core/core.func b/core/core.func
index fb6a394..05312ce 100644
--- a/core/core.func
+++ b/core/core.func
@@ -2741,7 +2741,7 @@ apt_conffile_report() {
   rm -f "$_CS_CONFFILE_GUARD"
   _CS_CONFFILE_GUARD=""
   unset APT_CONFIG
-  [[ -n "${added//[[:space:]]/}" ]] || return 0
+  [[ -n "${added//[[:space:]]/}" && -z "${_CS_CONFFILE_QUIET:-}" ]] || return 0
 
   msg_warn "Kept your version of these config files - upstream shipped changes to them too:"
   local f
diff --git a/lxc/install.func b/lxc/install.func
index 98b3f31..875257a 100644
--- a/lxc/install.func
+++ b/lxc/install.func
@@ -1371,6 +1371,10 @@ network_check() {
 # Updates container OS and sources appropriate tools.func
 # ------------------------------------------------------------------------------
 update_os() {
+  # Scripts write a package's config before installing it; dpkg then asked about
+  # the conffile with no terminal and the install failed.
+  _CS_CONFFILE_QUIET=1
+  declare -f apt_conffile_guard >/dev/null 2>&1 && apt_conffile_guard
   msg_info "Updating Container OS"
   configure_http_proxy